[commands] use __args__ and __origin__ where applicable

2 files changed, 27 insertions, 17 deletions

diff --git a/discord/ext/commands/core.py b/discord/ext/commands/core.py
index ab8c52c1..215c89b1 100644
--- a/discord/ext/commands/core.py
+++ b/discord/ext/commands/core.py
@@ -30,8 +30,6 @@ from typing import (
     Literal,
     Tuple,
     Union,
-    get_args as get_typing_args,
-    get_origin as get_typing_origin,
 )
 import asyncio
 import functools
@@ -86,6 +84,10 @@ def flatten_literal_params(parameters: Iterable[Any]) -> Tuple[Any, ...]:
             params.append(p)
     return tuple(params)
 
+def normalise_optional_params(parameters: Iterable[Any]) -> Tuple[Any, ...]:
+    none_cls = type(None)
+    return tuple(p for p in parameters if p is not none_cls) + (none_cls,)
+
 def _evaluate_annotation(tp: Any, globals: Dict[str, Any], cache: Dict[str, Any] = {}, *, implicit_str=True):
     if isinstance(tp, ForwardRef):
         tp = tp.__forward_arg__
@@ -102,6 +104,12 @@ def _evaluate_annotation(tp: Any, globals: Dict[str, Any], cache: Dict[str, Any]
     if hasattr(tp, '__args__'):
         implicit_str = True
         args = tp.__args__
+        if tp.__origin__ is Union:
+            try:
+                if args.index(type(None)) != len(args) - 1:
+                    args = normalise_optional_params(tp.__args__)
+            except ValueError:
+                pass
         if tp.__origin__ is Literal:
             if not PY_310:
                 args = flatten_literal_params(tp.__args__)
@@ -547,12 +555,13 @@ class Command(_BaseCommand):
             raise BadArgument(f'Converting to "{name}" failed for parameter "{param.name}".') from exc
 
     async def do_conversion(self, ctx, converter, argument, param):
-        origin = get_typing_origin(converter)
+        origin = getattr(converter, '__origin__', None)
 
         if origin is Union:
             errors = []
             _NoneType = type(None)
-            for conv in get_typing_args(converter):
+            union_args = converter.__args__
+            for conv in union_args:
                 # if we got to this part in the code, then the previous conversions have failed
                 # so we should just undo the view, return the default, and allow parsing to continue
                 # with the other parameters
@@ -568,12 +577,13 @@ class Command(_BaseCommand):
                     return value
 
             # if we're here, then we failed all the converters
-            raise BadUnionArgument(param, get_typing_args(converter), errors)
+            raise BadUnionArgument(param, union_args, errors)
 
         if origin is Literal:
             errors = []
             conversions = {}
-            for literal in converter.__args__:
+            literal_args = converter.__args__
+            for literal in literal_args:
                 literal_type = type(literal)
                 try:
                     value = conversions[literal_type]
@@ -591,7 +601,7 @@ class Command(_BaseCommand):
                     return value
 
             # if we're here, then we failed to match all the literals
-            raise BadLiteralArgument(param, converter.__args__, errors)
+            raise BadLiteralArgument(param, literal_args, errors)
 
         return await self._actual_conversion(ctx, converter, argument, param)
 
@@ -614,7 +624,7 @@ class Command(_BaseCommand):
         # The greedy converter is simple -- it keeps going until it fails in which case,
         # it undos the view ready for the next parameter to use instead
         if isinstance(converter, converters.Greedy):
-            if param.kind == param.POSITIONAL_OR_KEYWORD or param.kind == param.POSITIONAL_ONLY:
+            if param.kind in (param.POSITIONAL_OR_KEYWORD, param.POSITIONAL_ONLY):
                 return await self._transform_greedy_pos(ctx, param, required, converter.converter)
             elif param.kind == param.VAR_POSITIONAL:
                 return await self._transform_greedy_var_pos(ctx, param, converter.converter)
@@ -782,7 +792,7 @@ class Command(_BaseCommand):
             raise discord.ClientException(f'Callback for {self.name} command is missing "ctx" parameter.')
 
         for name, param in iterator:
-            if param.kind == param.POSITIONAL_OR_KEYWORD or param.kind == param.POSITIONAL_ONLY:
+            if param.kind in (param.POSITIONAL_OR_KEYWORD, param.POSITIONAL_ONLY):
                 transformed = await self.transform(ctx, param)
                 args.append(transformed)
             elif param.kind == param.KEYWORD_ONLY:
@@ -1074,7 +1084,7 @@ class Command(_BaseCommand):
         return ''
 
     def _is_typing_optional(self, annotation):
-        return get_typing_origin(annotation) is Union and get_typing_args(annotation)[-1] is type(None)
+        return getattr(annotation, '__origin__', None) is Union and type(None) in annotation.__args__
 
     @property
     def signature(self):
@@ -1094,13 +1104,14 @@ class Command(_BaseCommand):
             # for typing.Literal[...], typing.Optional[typing.Literal[...]], and Greedy[typing.Literal[...]], the
             # parameter signature is a literal list of it's values
             annotation = param.annotation.converter if greedy else param.annotation
-            origin = get_typing_origin(annotation)
+            origin = getattr(annotation, '__origin__', None)
             if not greedy and origin is Union:
-                union_args = get_typing_args(annotation)
-                optional = union_args[-1] is type(None)
-                if optional:
+                none_cls = type(None)
+                union_args = annotation.__args__
+                optional = union_args[-1] is none_cls
+                if len(union_args) == 2 and optional:
                     annotation = union_args[0]
-                    origin = get_typing_origin(annotation)
+                    origin = getattr(annotation, '__origin__', None)
 
             if origin is Literal:
                 name = '|'.join(f'"{v}"' if isinstance(v, str) else str(v) for v in annotation.__args__)
diff --git a/discord/ext/commands/errors.py b/discord/ext/commands/errors.py
index b825057e..98154d10 100644
--- a/discord/ext/commands/errors.py
+++ b/discord/ext/commands/errors.py
@@ -23,7 +23,6 @@ DEALINGS IN THE SOFTWARE.
 """
 
 from discord.errors import ClientException, DiscordException
-import typing
 
 
 __all__ = (
@@ -646,7 +645,7 @@ class BadUnionArgument(UserInputError):
             try:
                 return x.__name__
             except AttributeError:
-                if typing.get_origin(x) is not None:
+                if hasattr(x, '__origin__'):
                     return repr(x)
                 return x.__class__.__name__